A thickening acid is the main acid system of the acidification of the Lower Paleozoic carbonate reservoirs in CHANGQING gas field, which has high viscosity and good retarded, seam-making performance, long acid etching effect and good modification effect. However, the current thickening acid used in CHANGQING gas field exits problems that acidified residual acid solution can not be recycled, and a thickening time is long and other issues.
Since Schlumberger Dowell had introduced a viscoelastic surfactant-based cleaning fracturing fluid in 1997, the advent of viscoelastic surfactant technology has been widely used and promoted in the oil and gas field production measures. Domestic reports of cleaning fracturing fluids are not uncommon, and cleaning fracturing fluids are popular in oilfield applications because they are easy to prepare, without the need for adhesives and breakers, no damage and good for maintaining the permeability of the proppant pack compared to conventional polymer fracturing fluids. According to the experience of VES, a amphoteric surfactant-based viscoelastic acid which has a superior performance has developed in abroad in the past two years, and is successfully used in acid-fracturing. But the acid can not be recycled.
In the face of the increase in the proportion of compact carbonate reservoir resources, it is urgent to find new technologies to enhance the modification effect of compact carbonate reservoirs. In 2014, CHANGQING Oilfield Company developed a new type of cleaning thickening acid system, the system has good heat resistance, shear resistance, low filtration loss, slow speed, good corrosion inhibition performance, capable of continuous mixing and cleaning low damage and other performances and advantages. However, the thickening acid has a long thickening time and can not be recycled.
At present, research and application of the recovery of surfactant thickening acid has not yet appeared in the domestic, therefore there is of great prospect to develop and apply the direct mixing of the surfactant thickening acid and the reuse of residual acid.